DESCRIPTION (applicant's abstract): The acyl-CoA dehydrogenases (ACDs) are a family of evolutionarily related enzymes involved in the first step of the B-oxidation of fatty acids and in the intermediate metabolism of leucine, isoleucine and valine. Deficiencies of these enzymes are important causes of inherited defects of metabolism in humans. The long-range objective of this project has been to investigate important structure/function relationships in the ACD gene family. Our general hypothesis is that this information will afford a better understanding of genotype/phenotype correlations in patients with deficiencies of these enzymes. In previous funding periods, we have made significant strides in characterizing the structure, enzymatic properties, and biogenesis of isovaleryl-CoA dehydrogenase (IVD), as well as identifying numerous IVD mutations in patients with isovaleric acidemia. Specific aims for this renewal application include Aim 1: characterization of WD catalytic function; Aim 2: determination of amino acid residues and motifs important for stabilization of IVD homotetrainers; and Aim 3: elucidation of the mechanism of interaction of ACDs with electron transferring flavoprotein, the physiologic electron acceptor for these enzyme. Site specific mutagenesis directed by structural analysis and molecular modeling will be used to create mutant enzymes, and new biophysical techniques will be developed which will facilitate study of these properties. This work will lead to a more complete understanding of the ACD gene family, and ultimately, to an improved ability to diagnose and treat patients with deficiencies of these enzymes.